The U.S. has finally entered World War I, and Constance Kopp is doing intelligence work on the home front for the Bureau of Investigation while youngest sister and aspiring actress, Fleurette, travels across the country entertaining troops with song and dance. In France, Norma oversees her thwarted pigeon project for the Army Signal Corps. Her roommate is a nurse at the American field hospital, and when she is accused of stealing essential medical supplies, the intrepid Norma is on the case—her sixth, after Kopp Sisters on the March—to find the true culprit.